Composite phylosilicate adsorbent and process for preparation thereof

Abstract

Disclosed is a composite body comprising amorphous and porous silica or silica-alumina and a layer of an aluminum-containing phylosilicate formed on surfaces of primary particles of the silica or silica-alumina. This composite phylosilicate is obtained by reacting a water-soluble silicate, a water-soluble zinc salt or magnesium salt and a water-soluble aluminum salt or aluminate in an aqueous medium containing a sol or gel of silica or silica-alumina. This composite phylosilicate has a large specific surface area and a large pore volume and has both the properties of a solid acid and the properties of a solid base.

We claim: 
     
       1. A composite phylosilicate comprising amorphous and porous silica or silica-alumina and a layer of an aluminum-containing phylosilicate formed on surfaces of primary particles of said silica or silica-alumina and having, as a whole, a chemical composition represented by three-component oxide molar ratios of SiO 2  of 5 to 80 mole%, MO (M stands for an atom selected from the group consisting of zinc and magnesium) of 5 to 65 mole% and Al 2  O 3  of 1 to 60 mole%, an X-ray diffraction pattern in which there is no substantial peak at a spacing dx of 8.40 to 6.40 Å and there are peaks at a spacing dx of 2.71 to 2.56 Å and a spacing dx of 1.56 to 1.52 Å, a specific surface area of at least 200 m 2  /g, and a pore volume of at least 0.25 cc/g in pores having a pore diameter of 10 to 300 Å. 
     
     
       2. A composite phylosilicate as set forth in claim 1, which has substantially the same X-ray diffraction pattern as that shown in FIG. 1 of the accompanying drawings. 
     
     
       3. A composite phylosilicate as set forth in claim 1, wherein the aluminum-containing phylosilicate is fraipontite. 
     
     
       4. A composite phylosilicate as set forth in claim 1, wherein the aluminum-containing phylosilicate has a chemical structure represented by the following formula:   (Zn.sub.3-x Al.sub.x)(Si.sub.2-x Al.sub.x)O.sub.5 (OH)     wherein x is a number of from 0.1 to 1.75.   
     
     
       5. A composite phylosilicate as set forth in claim 1, which has, as a whole, a chemical composition represented by three-component oxide molar ratios of SiO 2  of 25 to 65 mole%, MO (M is an atom selected from zinc and magnesium) of 15 to 60 mole% and Al 2  O 3  of 2 to 50 mole%. 
     
     
       6. A composite phylosilicate as set forth in claim 1, wherein the divalent metal M is zinc alone. 
     
     
       7. A composite phylosilicate as set forth in claim 1, wherein the divalent metal M comprises zinc and magnesium at an atomic ratio of from 95/5 to 50/50. 
     
     
       8. A composite phylosilicate as set forth in claim 1, which has a Hunter whiteness higher than 90%. 
     
     
       9. A composite phylosilicate as set forth in claim 1, wherein the amorphous and porous silica or silica-alumina is present in an amount of 10 to 70% by weight based on the whole composite phylosilicate. 
     
     
       10. An adsorbent comprising a composite phylosilicate as set forth in claim 1. 
     
     
       11. A process for the preparation of a composite phylosilicate comprising amorphous and porous silica or silica-alumina and a layer of an aluminum-containing phylosilicate formed on surfaces of primary particles of said silica or silica-alumina as the carrier, said process comprising adding a water-soluble silica silicate, a water-soluble zinc salt and/or a water-soluble magnesium salt, and a water-soluble aluminum salt and/or a water-soluble aluminate to an aqueous medium containing a dispersion of a sol or gel of silica or silica-alumina to produce, as a whole, a chemical composition represented by three-component oxide molar ratios of SiO 2  of 5 to 80 mole%, MO (M stands for an atom selected from the group consisting of zinc and magnesium) of 5 to 65 mole% and Al 2  O 3  of 1 to 60 mole%, and reacting the added salts in the presence of said silica or silica-alumina. 
     
     
       12. A preparation process according to claim 11, wherein the dispersion of the sol or gel of silica or silica-alumina has a specific surface area of at least 200 m 2  /g in the dry state. 
     
     
       13. A preparation process according to claim 11, wherein the dispersion of the sol or gel of silica-alumina contains up to 80% by weight of Al 2  O 3 . 
     
     
       14. A preparation process according to claim 11, wherein the dispersion of the sol or gel of silica or silica-alumina is used as an amount of 10 to 70% by weight based on the composite phylosilicate. 
     
     
       15. A preparation process according to claim 11, wherein the solid concentration of silica or silica-alumina in the aqueous medium is 1 to 20% by weight. 
     
     
       16. A preparation process according to claim 11, wherein the reaction is carried out at a temperature in the range of from room temperature to 100° C. 
     
     
       17. A preparation process according to claim 11, wherein the reaction is carried out at a pH value of from 5 to 10.